1. Field of the Invention
The present invention relates to a projector, particularly relates to a projector having a cooling fan for maintaining temperature of a light source lamp at predetermined temperature.
2. Description of the Related Art
In a background art, there is known a projector having a cooling fan for maintaining temperature of a light source lamp at predetermined temperature (refer to, for example, JP-A-9-304834).
In JP-A-9-304834, mentioned above, there is disclosed a projector according to an example of the background art arranged with a lamp box provided with an exhausting fan (cooling fan) on a rear side of a light source lamp at inside of a cabinet and having an opening portion including a bimetal or a shape memory alloy for making an opening state variable by driving a fin in accordance with temperature at inside of the cabinet on a rear side of the lamp box. According to a structure disclosed in JP-A-9-304834, during a time period in which temperature at inside of the cabinet is low, leakage of light from a vent hole provided on a rear face of the cabinet is prevented with priority by narrowing an opening of the opening portion. Further, when temperature at inside of the cabinet rises, temperature rise at inside of the cabinet is restrained by facilitating to exhaust air from the lamp box by the exhausting fan by widening the opening of the opening portion in accordance with temperature rise.
FIG. 10 is a perspective view of a project or having a cooling fan for maintaining a light source lamp at predetermined temperature according to other example of the background art. FIG. 11 is a top view of the projector according to the other example of the background art shown in FIG. 10. FIG. 12 is a perspective view showing a light source lamp and a lamp case of the projector according to the other example of the background art. FIG. 13 is a sectional view of the light source lamp of the projector according to the other example of the background art shown in FIG. 12. An explanation will be given of a structure of a projector 100 according to the other example of the background art in reference to FIG. 10 through FIG. 13.
As shown by FIG. 10 and FIG. 11, the projector 100 according to the other example of the background art is provided with a lamp case holder 110, a light source lamp 120 including an ultra high pressure mercury lamp contained at inside of the lamp case of the holder 110, a lamp case 130 attached with the light source lamp 120, a coil spring 140 for fixing the light source lamp 120 to the lamp case 130, a projecting portion 150 for forming an image for projecting to a screen (not illustrated) by using light of the light source lamp 120, a cooling fan 160 arranged on a side of a side face of the light source lamp 120 for maintaining the light source lamp 120 at predetermined temperature, and a suction port 170 for supplying outside air to the cooling fan 160 at inside of the apparatus.
As shown by FIG. 12, the light source lamp 120 is fixed to the lamp case 130 by the coil spring 140. As shown by FIG. 13, the light source lamp 120 including the ultra high pressure mercury lamp includes a light source 121, a reflector 122 in a recessed shape for reflecting light from the light source 121 in a front direction, and a flange portion 123 provided at an end portion of the reflector 122. The light source 121 is provided at a center portion of the reflector 122.
Further, as shown by FIG. 11, the projecting portion 150 includes a light tunnel 151, a mirror 152, a lens 153, a DMD element 154, and a projecting lens 155. The light tunnel 151 is provided with a function of shaping light emitted from the light source lamp 120 in a rectangular shape. Further, the mirror 152 is provided for reflecting light in the rectangular shape shaped by the light tunnel 151 in a direction of arranging the DMD element 154. Light reflected by the mirror 152 is made to be incident on the DMD element 154 via the lens 153. Further, the DMD element 154 is an element for forming an image by controlling light incident on the DMD element 154. Further, the image formed by the DMD element 154 is projected to a screen (not illustrated) by passing the projecting lens 155.
Here, in the projector 100 according to the other example of the background art shown in FIG. 11, there is a drawback that whereas temperature of the light source lamp 120 including the ultra high pressure mercury lamp excessively rises, the light source 121 is destructed, when temperature of the light source lamp 120 falls excessively, a brightness is reduced. Therefore, in the projector 100 according to the other example of the background art, in operating the projector 100, the light source lamp 120 is maintained always at predetermined temperature (about 400 .C through about 500 .C) by the cooling fan 160 and a temperature sensor (not illustrated).
However, in the projector according to the other example of the background art, when the projector 100 stops to operate, also the cooling fan 160 stops to operate. Therefore, there is brought about a drawback that immediately after stopping to operate the projector 100, temperature at an other peripheral face of the light source lamp 120 rapidly rises by residual heat of the light source 121 of the light source lamp 120. The rapid temperature rise of the outer peripheral face of the light source lamp 120 constitutes a factor of bringing about a thermal deterioration, deformation or the like of a part at a surrounding of the light source lamp 120. Therefore, according to the projector 100 of the background art, there is a drawback that it is necessary to form the part or the cabinet made of resin arranged at the surrounding of the light source lamp 120 by an expensive heat resistant material. Thereby, there poses a problem that product cost is increased.
Further, according to the structure disclosed in JP-A-9-304834, mentioned above, the opening portion including a bimetal or a shape memory alloy an opening degree of which is increased by temperature rise is arranged at a position on a side of the exhausting fan opposed to the light source lamp and remote from the light source lamp and therefore, it is difficult to directly restrain temperature rise of the light source lamp by the opening portion. Therefore, when the exhausting fan is stopped by stopping to operate the projector in the structure disclosed in JP-A-9-304834, mentioned above, similar to the projector 100 of the other example of the background art shown in FIG. 11, there is brought about a drawback that rapid temperature rise is brought about at the outer peripheral face of the light source lamp immediately after stopping the exhausting fan by stopping to operate the projector. Therefore, also in JP-A-9-304834, mentioned above, similar to the projector 100 according to the other example of the background art shown in FIG. 11, there poses a problem that thermal deterioration, deformation or the like of the part is brought about at the surrounding of the light source lamp owing to rapid temperature rise of the outer peripheral face of the light source lamp.